Method of designing active region pattern with shift dummy pattern

ABSTRACT

A method of designing an active region pattern with a shifted dummy pattern, wherein an integrated circuit having an original active region pattern thereon is provided. The original active region pattern is expanded with a first parameter of line width to obtain a first pattern. By subtracting the first pattern, a second pattern is obtained. A dummy pattern which comprises an array of a plurality of elements is provided. By shifting the elements, a shifted dummy pattern is obtained. The second pattern and the shifted dummy pattern are combined, so that an overlapped region thereof is extracted as a combined dummy pattern. The combined dummy pattern is expanded with a second parameter of line width, so that a resultant dummy pattern is obtained. The resultant dummy pattern is added to the first pattern, so that the active region pattern with a shifted dummy pattern is obtained.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the priority benefit of Taiwan application serial no. 87107569, filed May 15, 1998, the full disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates in general to a method of designing an active region pattern with a shift dummy pattern, and more particularly, to a method adding a shift dummy pattern into an diffusion region for the process of forming a shallow trench isolation. Therefore, a better planarization effect is obtained in the subsequent process of chemical mechanical polishing (CMP), and a circuit problem induced by various parasitic capacitors is resolved.

[0004] 2. Description of the Related Art

[0005] As the design of an integrated circuit is more and more complex, the line width of fabrication process reduced narrower than 1 μm causes a restriction the development of a trench isolation technique in a complementary metal-oxide-semiconductor (CMOS) is thus restricted. While performing chemical mechanical polishing for planarization, if a under layer has a pattern on which the distance between devices is over 10 μm, a dishing recess is formed on the region without a device thereon after polishing. Thus, a global planarization is affected. This is called as a dishing effect. In FIG. 1A to FIG. 1D, a shallow trench isolation formed by a conventional technique of chemical mechanical polishing is shown.

[0006] In FIG. 1A, on a semiconductor substrate 10, for example, a silicon substrate, a pad oxide layer 11 and a dielectric layer 12, for example, a silicon nitride layer are formed in sequence. Using photolithography and etching, a device region 13 is formed on the substrate 10. Using a photo-resist layer (not shown) on the device region 13 as a mask, the substrate 10 is etched, for example, by anisotropic etching, to form several trenches with certain depths. In FIG. 1B, using chemical vapor deposition (CVD), an oxide layer 14 is formed over the substrate 10. The oxide layer 14 is polished by chemical mechanical polishing with the dielectric layer 12 as a stop layer, so that several trench isolations 15, 16 are formed as shown in FIG. 1C.

[0007] After the formation of trench isolations 15, 16, subsequent processes, for example, removing the pad oxide layer 11 and the dielectric layer, forming a gate oxide layer 17 and a poly-silicon layer 18, is performed as shown in FIG. 1D. As shown in the figure, the width of each trench isolation is not identical. For example, the region of trench isolation 16 is larger than the region of the trench isolation 15. The polysilicon layer 18 is well planarized on the trench isolation 15. On the contrary, the poly-silicon layer 18 on the trench isolation 15 has a smooth recess. Thus, using chemical mechanical polishing, only a local planarization is achieved. The global planarization cannot be achieved.

[0008] To resolve the drawback mentioned above, conventionally, a dummy pattern is added to the active region pattern to improve the uniformity of chemical mechanical polishing. However, a parasitic capacitance is induced by doing so to affect the performance of devices. The metal line on different dummy pattern causes a time delay by different parasitic capacitance, and therefore, causes a circuit problem. In FIG. 2, a conventional method of designing an active region pattern with a dummy pattern is shown. Metal lines 20, 22 are formed on different locations of the dummy pattern 24, and the dummy pattern 24 comprises columns 24 a to 24 d. For example, the metal line 20 is formed on a column 24 c of the dummy pattern, and the metal line 22 covers a part of the column 24 a and a part of the column 24 b of the dummy pattern 24. Between the metal line 22 and the dummy pattern 24, different parasitic capacitance is induced in practical application, so that a problem of different time order, for example, an RC delay is caused.

SUMMARY OF THE INVENTION

[0009] It is therefore an object of the invention to provide a method of designing an active region pattern with a dummy pattern. By shifting a predetermined dummy pattern, the parasitic capacitance between each metal line and the dummy pattern is identical. Therefore, an identical RC time is obtained.

[0010] To achieve these objects and advantages, and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention is directed towards a method of designing an active region pattern with a dummy pattern. An integrated circuit having an original active region pattern thereon is provided. The original active region pattern is expanded with a first parameter of line width to obtain a first pattern. By subtracting the first pattern, a second pattern is obtained. A dummy pattern which comprises an array of a plurality of elements is provided. By shifting the elements, a shifted dummy pattern is obtained. The second pattern and the shifted dummy pattern are combined, so that an overlapped region thereof is extracted as a combined dummy pattern. The combined dummy pattern is expanded with a second parameter of line width, so that a resultant dummy pattern is obtained. The resultant dummy pattern is added to the first pattern, so that the active region pattern with a shifted dummy pattern is obtained.

[0011] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 to FIG. 1D shows a method of forming a shallow trench isolation by employing a conventional chemical mechanical polishing technique;

[0013]FIG. 2 shows a conventional active region pattern with a dummy pattern;

[0014]FIG. 3 shows an active region pattern with a shifted dummy pattern in a preferred embodiment according to the invention;

[0015]FIG. 4 shows an original pattern designed in a preferred embodiment according to the invention;

[0016]FIG. 5 shows a reverse pattern from expanding the original pattern shown in FIG. 4 with parameters of a and b;

[0017]FIG. 6A shows a dummy pattern designed in a preferred embodiment according to the invention;

[0018]FIG. 6B shows a shifted dummy patterned of the dummy pattern shown in FIG. 6A;

[0019]FIG. 7A shows a combined pattern of the patterns shown in FIG. 5 and FIG. 6B;

[0020]FIG. 7B shows an expansion of the combined pattern shown in FIG. 7A; and

[0021]FIG. 8 shows an active region pattern with a dummy pattern in a preferred embodiment according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022]FIG. 3 shows an active region pattern with a shifted dummy pattern in a preferred embodiment according to the invention. As shown in FIG. 3, metal lines 30, 32 covers different parts of a dummy pattern 34. Since the dummy pattern is shifted as a certain pattern, so that the parasitic capacitance between the metal line 30 and the dummy pattern 34 is identical the parasitic capacitance between the metal line 32 and the dummy pattern 34. As a consequence, in practical circuit application, a better performance is obtained without a RC time delay problem.

[0023] An original active pattern used in a preferred embodiment according to the invention is shown in FIG. 4. The original active pattern comprises patterns of, for example, a device region 40, poly-silicon layer 42, and well region 44.

[0024]FIG. 5 shows a reverse pattern of the original pattern shown in FIG. 4 with a parameters of a and b. The device region pattern 40 and the poly-silicon pattern 42 are expanded with a line width of a, for example, 1.4 μm. The margin of the well region 44 is expanded inwardly and outwardly with a parameter of line width b of, for example, 0.9 μm. While the device region pattern 40, the poly-silicon region 42 and the well region overlap with one another due to expansion, the patterns of these regions merge as a first region pattern 50. By reverse logic calculation (NOR operation), for example, reverse tone, a second region pattern 52 is obtained by subtracting the first region pattern 50.

[0025]FIG. 6A shows a dummy pattern 60 employed in this embodiment according to the invention. The dummy pattern 60 comprises an array of a plurality of elements. The elements are equidistantly spaced with a distance of d, for example, 1.8 μm. Each element of the array has a width of e and a length of f, for example, 0.2 μm. and 2.2 μm. respectively.

[0026] In FIG. 6B, a dummy pattern 60 a is shown by shifting the dummy pattern shown in FIG. 6A in both longitudinal and transverse directions with a certain distance, for example, 0.2 μm.

[0027] In FIG. 7A, combining the patterns shown in FIG. 5 and FIG. 6B, an overlapped region of the second region pattern 52 in FIG. 5 and the shifted dummy pattern 60 a in FIG. 6b is extracted as a combined pattern 70. That is, an AND operation is performed to extract the combined pattern 70 from the patterns shown in FIG. 5 and FIG. 6B.

[0028] The combined pattern 70 shown in FIG. 7A is then expanded with a parameter of line width c, for example, 0.4 μm. The resultant dummy pattern 70 a is shown as FIG. 7B.

[0029] By adding the resultant dummy pattern 70 a into the original active region pattern shown in FIG. 4, an active region pattern with a dummy pattern 80 is formed and shown in FIG. 8. The active region pattern with a dummy pattern 80 is then applied in chemical mechanical polishing technique for forming shallow trench isolation.

[0030] One advantage of the invention is that by adding the dummy pattern to the active region pattern, the large isolation region is partitioned by the dummy pattern, so that the possibility of forming a recess is suppressed.

[0031] A further advantage of the invention is that by adding a shifted dummy pattern, an identical parasitic capacitance is obtained between the active region pattern and each of the metal lines formed subsequently. Therefore, an equivalent RC time delay caused between each metal line and the active region pattern is obtained. The performance of the device is thus upgraded.

[0032] Other embodiment of the invention will appear to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples to be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims. 

What is claimed is:
 1. A method of designing an active region pattern with a shifted dummy pattern, wherein an integrated circuit having an original active region pattern thereon is provided, the method comprising: expanding the original active region pattern with a first parameter of line width to obtain a first pattern; subtracting the first pattern, so that a second pattern is obtained; providing a dummy pattern which comprises an array of a plurality of elements; shifting the elements to obtained a shifted dummy pattern; combining the second pattern and the shifted dummy pattern, so that an overlapped region thereof is extracted as a combined dummy pattern; expanding the combined dummy pattern with a second parameter of line width, so that a resultant dummy pattern is obtained; and adding the resultant dummy pattern to the first pattern, so that the active region pattern with a shifted dummy pattern is obtained.
 2. The method according to claim 1, wherein the original active region pattern further comprises a device region pattern, a poly-silicon pattern, and a well region pattern, wherein the device region pattern and the poly-silicon pattern are expanded with the first parameter of line width; and the well region pattern is expanded with a third parameter of line width.
 3. The method according to claim 2, wherein the third parameter of line width is about 0.9 μm.
 4. The method according to claim 1, wherein the first parameter of line width is about 1.4 μm.
 5. The method according to claim 1, wherein the second parameter of line width is about 0.4 μm.
 6. A method of designing an active region pattern with a shifted dummy pattern, comprising: providing an integrated circuit, on which at least an active region pattern, a polysilicon region pattern and a well region pattern are included; expanding the active region pattern with a first parameter of line width; expanding the poly-silicon pattern with a second parameter of line width; expanding the well region pattern with a third parameter of line width; combining the expanded active region pattern, the expanded poly-silicon pattern, and the well region pattern as a first pattern; performing an NOR operation, so that the first pattern is subtracted to leave a second pattern on the integrated circuit; providing a dummy pattern which comprises an array of a plurality of elements; shifting the elements to obtained a shifted dummy pattern; performing an AND operation, so that an overlapped region of the second pattern and the shifted dummy pattern is extracted as a combined dummy pattern; expanding the combined dummy pattern with a fourth parameter of line width, so that a resultant dummy pattern is obtained; and performing an OR operation, so that the resultant dummy pattern is added to the first pattern, therefore, the active region pattern with a shifted dummy pattern is obtained. 